Flame responsive device using plugged compensatory tube



June 24, 1958 ATOR FLAME RESPONSIVE DEVICE USING PLUGGED COMPENSATORY TUBE Filed Jan. 8, 1954- IN V EN TOR.

prraeA/a q United States Patent The present invention relates to means and techniques for detecting the presence of a flame and for controlling 1 q the flow of fuel to such flame. I The problem of detecting the presence of a flame in furnace gives rise to certain difficulties, mainly, because the radiation from the heated walls of the furnace may, unless certain precautions are taken, have the same effect as the radiation from the flame itself, with the result that a false indication may be produced, leading to the creation of a dangerous situation. a V

Briefly, the present invention relates to improved means and techniques for producing an indication or control which takes into account the radiation from the heated furnace walls as well as the radiation from the flame, by establishing a certain differential effect, such differential effect being essentially in accordance with the difference in radiation, due on the one hand, to the flame itself and, on the other hand due to a body heated by the flame.

For this purpose two photocells are provided, one to receive radiation from the flame and furnace wall, and the other photocell being arranged to receive radiation from a body which is heated by the flame to a temperature comparable to the temperature of the furnace wall. The radiations as measured by the'two photocells are electrically subtracted so as to produce a net result, i. e., a net voltage which has a relatively large value when a flame is present and which has a relatively small value or zero value when there is no flame, such net voltage being amplified and used to produce either an indication or to control the flow of fuel to the flame.

It is, therefore, a general object of the present invention to provide means and techniques of the character indicated above.

A specific object of the present invention is to provide improved means and techniques of this character which requires no moving elements.

Another specific object of the present invention is to provide improved means and techniques of this character which requires the use of only one relatively small viewing aperture in the furnace wall.

Another specific object of the present invention is to provide means and techniques of this character which is relatively insensitive to sporadic fluctuations in intensity of the flame.

The features of the present invention which are believed to be novel are set forth with particularity in the appended claims. This invention itself, both as to its organization and manner of operation, together with further objects and advantages thereof, may be best understood by reference to the following description taken in connection with the accompanying drawings in which:

The single figure of the drawing illustrates a conventional furnace with associated conventional flame-producing means with apparatus embodying the features of the present invention, the apparatus being shown partly in structural form and partly in schematic form.

The furnace is of conventional construction and is considered to be lined with firebrick and is defined by the four walls 12, 13, 14 and 15. The conventional flame producing means 16 serves to produce the flame 17, such flame-producing means being supplied with fuel which normally flows from the fuel inlet 20 through the solenoid valve 21 to the fuel outlet 22, such outlet being deemed to be in communication with the conventional apparatus a The flame 17 may be considered as that being due either to the burning of oil or to the burningof gas.

Two radiation channels are provided, namely, radi-- The tube 25 is oriented so as to receive the radiation not' only from the flame 17, but also from the heated furnace wall 13 along a 'path indicated by the line 28, such' radiation being focused bya condensing lens 29 and apation channels 25 and 26 in the form of tubes.

plied through a suitable filter 30 onto the photocell 32.

The other radiation tube 26 has one of its ends closed; by a circular refractory plug 33 and the other one of its ends in communication with the photocell 34. A lens 37 that order, between and filter 38 are optically disposed in the tube 26 and the photocell 34.

The plug 33 of refractory material is heated to an incandescent state by the flame 17 to substantially the same i temperature as the temperature of the furnace wall. Both tubes 25, 26 extend into the same opening 40 in the box, of course, being in communication with the open ends of tubes 25 and 26. r

The photocell 32 is energized electrically to produce an electrical quantity which represents the combined radia-- tion of the flame and the furnace wall; while the photocell 34 is energized electrically to produce an electrical quantity which represents the radiation from the furnace wall itself, it being assumed that for all'practical purposes the plug 33 may be considered to represent the furnace wall itself.

In order to achieve the aforementioned differential effect, the electrical outputs of the two photocells 32 and 34 are subtracted and it is understood, that while different means may be employed to obtain such subtraction, the bridge circuit as now described is preferred. The anode of both tubes 32 and 34 are each connected to the positive terminal of source 60 which has its negative terminal connected to the cathodes of tubes 32 and 34 through resistances 62 and 63, respectively. The cathode of tube 32 is grounded While the cathode of tube 34 is connected to the ungrounded input terminal of the direct current amplifier 66. The output of the amplifier 66 is applied to conventional control circuit 68 which includes a relay for controlling the energization of the solenoid valve 21.

It is understood that in the presence of a flame, the solenoid valve 21 is energized to allow the flow of fuel to the burner 16; and, when the flame 17 is extinguished for any reason whatsoever, the solenoid valve 21 is deenergized to allow the spring means normally associated by the flame, namely, the body or plug 33. These two electrical quantities developed across resistances 62 and 63 are effectively compared and their resultant, a third electricalquantity is applied to the input terminals of the amplifier 66 to control the flow of fuel to the flame or to the flame-producing means 16.

While the particular embodiments of the present in Patented June i 24, 19 58 f The various lenses, filters and photocells are enclosed within a light-tight rectangularibox 43, such vention have, been shown and described, it'will'be obvious to those skilled in the art that changes and modifications may be made without departing from this invention in its broader aspects and, therefore, the aim in the appended, claims ,is to cover all such, changes and modificationsas fallwithin their scope,

1, In apparatus for detecting thepresence of a, flame, means for producing, saidflame, an enclosure having a bodyheated by said,flame,jsaid, enclosure having a single,

photocell means, in communication with said secondtubeior receiving radiation from said: body which plugsasaid seconddight tube, said second photocell means producing an electrical .quantity representative of the radiation from said body plugging said. secondrtube, means for comparing the first and. second electrical quantities to derive a third, electrical quantity, means controlling the flow of, fuel to, said: flame producing means in accordance with the said third electrical quantity.

, 2i, ,ln.,apparatlls for detecting the presence of a flame, means; for producing said flame, an enclosure having a body heated by said flame, said enclosure having a viewing aperture, a first light tube for viewing said flame and said '4' body, a second light tube aligned with said aperture, a plug in said second light tube and heated by said flame, means responsive to the radiation transmitted through said first and second tubes and controlling the flow of fuel to said flame producing means.

3. In apparatus for detecting the presence of a flame, means for producing said flame, an enclosure having a body heated by said flame, a pair of light tubes, one of said light tubes viewing said flame and said body heated by said flame, the other light tube having a plug near one end thereof and heated by said flame, and means sensitive to the radiation transmitted through both said tubes for controlling the flow of fuel to said flame producing means. a

4. Apparatus as set forth in claim 1 in which the lastmentioned meanscuts off the flowrof fuel to the flame upon extinguishment of the flame.

5. Apparatus as set forth in claim 2 in which the lastmentioned, means cuts off the flow of fuel to the flame upon extinguishment of the flame.

6. Apparatus as set forth in claim 3 in which the lastmentioned means cuts off the flow of fuel to the flame uponextinguishment of the flame.

, References Cited in the file of this patent UNITED STATES PATENTS 

